Key Takeaway
Exogenous ketone supplements show no consistent benefit for running performance, though they may enhance fat oxidation and spare glycogen during endurance running.
Summary
This systematic review evaluated the effects of both ketogenic diets and exogenous ketone supplements on the aerobic performance of endurance runners. The review specifically focused on running as the exercise modality, distinguishing it from the broader ketone-and-exercise literature that predominantly uses cycling protocols.
The authors systematically searched for studies examining ketone interventions in runners, assessing outcomes including time trial performance, VO2max, running economy, substrate utilization, and perceived exertion. For exogenous ketone supplements specifically, the evidence showed no consistent performance improvements in running-specific outcomes. However, metabolic changes were observed, including shifts toward greater fat oxidation and potential glycogen sparing during prolonged efforts.
The review highlights important distinctions between ketogenic diets and exogenous ketone supplements as interventions, and between cycling and running as exercise modalities. The authors note that running may impose unique physiological demands (weight-bearing, thermoregulation, biomechanics) that could influence how ketone metabolism affects performance. The lack of consistent performance benefits suggests that any metabolic advantages from ketone availability may not translate into meaningful performance gains for runners under typical race conditions.
Methods
Systematic review following PRISMA guidelines. Electronic databases were searched for studies examining the effects of ketogenic diets and/or exogenous ketone supplements on endurance running performance. Inclusion criteria required studies with endurance runners as participants and aerobic performance outcomes. Studies were assessed for risk of bias and categorized by intervention type (ketogenic diet vs. exogenous ketone supplement) and outcome measures.
Key Results
- Exogenous ketone supplements did not consistently improve running time trial performance or VO2max
- Increased fat oxidation was observed with both ketogenic diets and exogenous ketone supplements during running
- Some evidence of glycogen sparing during prolonged running efforts with exogenous ketones
- Ketogenic diets tended to impair high-intensity running performance despite enhancing fat oxidation
- Running economy results were inconsistent across studies
- Perceived exertion was generally unaffected by ketone supplementation
Limitations
- Limited number of studies specifically examining exogenous ketones in runners (most ketone research uses cycling)
- Heterogeneity in supplement types, doses, and running protocols across included studies
- Many included studies had small sample sizes
- Mix of trained and recreational runners across studies limits generalizability
- Short-duration interventions may miss adaptation effects
- Combined analysis of ketogenic diets and supplements, despite different mechanisms of action